although the stats are a useful tool and you can learn from the data, perhaps the start point should be to establish what you want from each session first and thus working to a structured plan is therefore important to achieve this...
_________________www.appliedtri.co.uk Tri and Du coaching

Are you getting faster?
How do you measure this?
When are your test sessions? How often?
Are you recovering faster?
Are you improving equally over all three disciplines?
Are you paticulary slow at anything? If so how can you improve?
Most importantly are you enjoying it? If its a real pain in the as take a few days, the urge to train will come back.

The data should be improving gradually, or indeed staying the same for less effort from yourself.
My watts are static but I'm slowly loosing weight, which greatly helps my running.

So ignoring completely the "properly structured training plan" (personally I think they're a bad idea, since you cannot predict even day to day variation, let alone where you might be in a week or month, but lowest common denominator plans would still be better than doing nothing of course if that is the alternative. )

What you get from the data, is a record of what you actually did, at its most basic you can track improvement, best to ensure you have lots of benchmark activities that make the comparison easy. Above that you yes need to look for patterns, short term that might hint if you're training too much, or can actually train more, especially if you've previously trained more without having any problems - you will be able to train more again.

Using some method to quantify overall training volume will help with that of course.

The next, which is less important in a 70.3, as you'll be doing so few maximal efforts or races in your triaining, is using the data to inform why you failed in a particular race (or hard session) did you push too hard riding over hills, did you under eat etc. You'll need to compare the efforts against similar successful and other failed activities to understand what went wrong etc.
_________________Jibbering Sports Stuff

Yeah, I'd agree. There's a lot of dick measuring that goes on with strava, but I have the segment leaderboards defaulted to just list my own performances. It's a very quick an easy way to check/quantify progress (or regression!) on some key loops/sections of road.

Being able to quickly see pace/speed, HR, power, etc is a nice way to put the numbers in context too. For example, I might have done a section slower, but if my power matched my best with a lower HR, I can infer the time was just a consequence of poor conditions rather than reduced performance.

So ignoring completely the "properly structured training plan" (personally I think they're a bad idea, since you cannot predict even day .

which is why elite athletes are so bad i suppose...

Then you would be getting into definitions of what a "structured training plan" is, but they certainly do not have the workouts planned weeks in advance at specific power or HR levels, which is what amateurs call a structured training plan.. The training is adapted on a much more local day to day depending on previous demands.
_________________Jibbering Sports Stuff

So ignoring completely the "properly structured training plan" (personally I think they're a bad idea, since you cannot predict even day .

which is why elite athletes are so bad i suppose...

Then you would be getting into definitions of what a "structured training plan" is, but they certainly do not have the workouts planned weeks in advance at specific power or HR levels, which is what amateurs call a structured training plan.. The training is adapted on a much more local day to day depending on previous demands.

absolutely...structured simply means organised and deliberate, and, whilst i am not a huge fan of long term plans, they at least act as a guide which athletes can follow..their usefulness comes in the athlete's ability to refine them locally...which, oddly enough, is what happens at elite level...
_________________www.appliedtri.co.uk Tri and Du coaching

So ignoring completely the "properly structured training plan" (personally I think they're a bad idea, since you cannot predict even day .

which is why elite athletes are so bad i suppose...

Then you would be getting into definitions of what a "structured training plan" is, but they certainly do not have the workouts planned weeks in advance at specific power or HR levels, which is what amateurs call a structured training plan.. The training is adapted on a much more local day to day depending on previous demands.

absolutely...structured simply means organised and deliberate, and, whilst i am not a huge fan of long term plans, they at least act as a guide which athletes can follow..their usefulness comes in the athlete's ability to refine them locally...which, oddly enough, is what happens at elite level...

Is it not also easier for Elites to be more rigid as essentially this their day job? For the majority of us it's a hobby so work, family etc have to be factored in.

So ignoring completely the "properly structured training plan" (personally I think they're a bad idea, since you cannot predict even day .

which is why elite athletes are so bad i suppose...

Then you would be getting into definitions of what a "structured training plan" is, but they certainly do not have the workouts planned weeks in advance at specific power or HR levels, which is what amateurs call a structured training plan.. The training is adapted on a much more local day to day depending on previous demands.

absolutely...structured simply means organised and deliberate, and, whilst i am not a huge fan of long term plans, they at least act as a guide which athletes can follow..their usefulness comes in the athlete's ability to refine them locally...which, oddly enough, is what happens at elite level...

Is it not also easier for Elites to be more rigid as essentially this their day job? For the majority of us it's a hobby so work, family etc have to be factored in.

absolutely...but some of that can be factored in during the planning, hence the point above about refining the plan..

elites don't train that much more (with exceptions) they rest more..
_________________www.appliedtri.co.uk Tri and Du coaching

So ignoring completely the "properly structured training plan" (personally I think they're a bad idea, since you cannot predict even day .

which is why elite athletes are so bad i suppose...

Then you would be getting into definitions of what a "structured training plan" is, but they certainly do not have the workouts planned weeks in advance at specific power or HR levels, which is what amateurs call a structured training plan.. The training is adapted on a much more local day to day depending on previous demands.

absolutely...structured simply means organised and deliberate, and, whilst i am not a huge fan of long term plans, they at least act as a guide which athletes can follow..their usefulness comes in the athlete's ability to refine them locally...which, oddly enough, is what happens at elite level...

Is it not also easier for Elites to be more rigid as essentially this their day job? For the majority of us it's a hobby so work, family etc have to be factored in.

absolutely...but some of that can be factored in during the planning, hence the point above about refining the plan..

elites don't train that much more (with exceptions) they rest more..

Rest and recovery, the key. Something I probably don't do very well!

Saying that, off work today and yesterday with a stinking cold, not been able to do much else apart from rest.